Problem: A bag contains $10$ red jelly beans, $5$ green jelly beans, and $4$ blue jelly beans. If a jelly bean is randomly chosen, what is the probability that it is not blue?
There are $10 + 5 + 4 = 19$ jelly beans in the bag. There are $4$ blue jelly beans. That means $19 - 4 = 15$ are not blue. The probability is $ \frac{15}{19}$.